Vehicles such as electric vehicles (EV) and plug-in hybrid vehicles (PHV) include rechargeable batteries as a power storage device that stores power to be supplied to a motor for driving. The rechargeable batteries may include an electrode assembly and a case. The electrode assembly includes positive electrodes and negative electrodes stacked on one another with separators located in between. The case accommodates the electrode assembly. The case is formed by welding a case body and a lid as in Patent Document 1.
As shown in FIG. 8, a case body 81 before welding has a tubular shape with an opening on the top surface thereof. A first protrusion 82 protrudes from an outer surface 81a of the case body 81 around the entire circumference of the case body 81. Further, a lid 83 before welding has a size such that the lid 83 is supported on an opening end surface of the case body 81. The lid 83 also has a portion to be inserted into the case body 81. A second protrusion 84 protrudes from an outer surface 83a of the lid 83 around the entire circumference of the lid 83.
When the case is manufactured, an inserted portion 86, which is a part of the lid 83, is inserted into the case body 81 and the outer circumferential portion of the lid 83 is placed on the opening end surface of the case body 81. Further, the outer surface 81a of the case body 81 and the outer surface 83a of the lid 83 are arranged to be flush with each other, such that the first protrusion 82 and the second protrusion 84 constitute a protrusion 85. Then the protrusion 85 is irradiated with a laser beam to become a part of a weld zone, so that the case body 81 and the lid 83 are welded together, thereby forming the case.